The wealth of information available in Raman spectra has led to accurate quantification of molecular and morphological components embedded in complex biological samples. The great interest in Raman spectroscopy lies in its potential for accurate and real time clinical diagnosis for a wide variety of diseases such as malignant tumors (cancers) and vulnerable arterial plaques (atherosclerosis). In addition, near-infrared (NIR) Raman spectroscopy can be employed for non-invasive applications such as continuous monitoring of glucose in diabetics and creatinine and urea in neonates and patients in intensive care units.
While successful application in terms of tissue classification as well as analyte concentration prediction has been achieved in several in vitro, animal model and even human subject studies, few of the promising results have been translated into clinical practice. This is in sharp contrast to its widespread applications in the process monitoring industry. The lack of similar usage in the health-care and medical devices sector can be attributed to two primary factors, namely the lack of robustness in Raman diagnostic methods that results in unsuccessful calibration transfer from one human subject to another. This is a direct consequence of the presence of spurious correlations in the diagnostic analysis between the analyte of interest and the spectral interferents, and further, the large spatial footprint of the developed Raman systems, which prevents its usage in a clinical facility. This factor is even more pronounced when a diagnostic tool has to be developed for a home user such as continuous blood glucose monitoring, where its feasibility is dependent on the convenience of the device, as well as its cost. Typically, the reduction in the size of a Raman system is constrained by the light source (e.g. NIR laser) and the spectrograph. Since Raman signals are intrinsically weak, the CCD detectors are often (especially for NIR Raman spectroscopy) cooled to reduce thermal and dark current noise. The additional cooling element also adds to the size of the clinical instrument. Further improvements are needed for both clinical and laboratory use.